SWEENY, TX --Efforts to clean residue off of transmission equipment that caused a series of power outages at several Southeast Texas refineries last month might have led to another power outage at a different facility on Tuesday. ConocoPhillips' refinery in Sweeny lost power at 11:15 a.m. Tuesday, said company spokesman Rich Johnson. Power was restored by 1 p.m. "We're in the process of restarting the affected units. No injuries or offsite impact was reported. The cause of power outage still under investigation," he said. The refinery in Sweeny, located about 65 miles southwest of Houston, can process up to 247,000 barrels per day. Late last month, several refineries in Texas City, located southeast of Houston, experienced a series of power outages. The electricity provider, Texas New Mexico Power Co., said those outages were caused by salt and other residue that had built up on transmission equipment at substations and other locations, leading to short circuits. Texas New Mexico Power spokeswoman Cathy Garber said since last month's outages, the electricity provider has been cleaning the residue off of all its transmission equipment in Southeast Texas. On Tuesday, workers had finished cleaning some of this equipment at the refinery in Sweeny and were in the process of powering it back on when something went wrong, Garber said. The problem might have been on the "refinery side of things" but officials are still trying to determine what exactly caused the outage, she said. The temporary shutdown of the refinery in Sweeny prompted the facility's flare system to burn off any chemical releases that might have been sent into the air. "We are conducting air monitoring in the area to insure there was no health risk in the community," Johnson said.